Cover Crop Roots Research Articles

Cover crop root exudates impact soil microbiome functional trajectories in agricultural soils

BackgroundCover cropping is an agricultural practice that uses secondary crops to support the growth of primary crops through various mechanisms including erosion control, weed suppression, nutrient management, and enhanced biodiversity. Cover crops may elicit some of these ecosystem services through chemical interactions with the soil microbiome via root exudation, or the release of plant metabolites from roots. Phytohormones are one metabolite type exuded by plants that activate the rhizosphere microbiome, yet managing this chemical interaction remains an untapped mechanism for optimizing plant-soil-microbiome interactions. Currently, there is limited understanding on the diversity of cover crop phytohormone root exudation patterns and our aim was to understand how phytochemical signals selectively enrich specific microbial taxa and functionalities in agricultural soils.ResultsHere, we link variability in cover crop root exudate composition to changes in soil microbiome functionality. Exudate chemical profiles from 4 cover crop species (Sorghum bicolor, Vicia villosa, Brassica napus, and Secale cereal) were used as the chemical inputs to decipher microbial responses. These distinct exudate profiles, along with a no exudate control, were amended to agricultural soil microcosms with microbial responses tracked over time using metabolomes and genome-resolved metatranscriptomes. Our findings illustrated microbial metabolic patterns were unique in response to cover crop exudate inputs over time, particularly by sorghum and cereal rye amended microcosms. In these microcosms, we identify novel microbial members (at the genera and family level) who produced IAA and GA4 over time. Additionally, we identified cover crop exudates exclusively enriched for bacterial nitrite oxidizers, while control microcosms were discriminated for nitrogen transport, mineralization, and assimilation, highlighting distinct changes in microbial nitrogen cycling in response to chemical inputs.ConclusionsWe highlight that root exudate amendments alter microbial community function (i.e., N cycling) and microbial phytohormone metabolisms, particularly in response to root exudates isolated from cereal rye and sorghum plants. Additionally, we constructed a soil microbial genomic catalog of microorganisms responding to commonly used cover crops, a public resource for agriculturally relevant microbes. Many of our exudate-stimulated microorganisms are representatives from poorly characterized or novel taxa, revealing the yet to be discovered metabolic reservoir harbored in agricultural soils. Our findings emphasize the tractability of high-resolution multi-omics approaches to investigate processes relevant for agricultural soils, opening the possibility of targeting specific soil biogeochemical outcomes through biological precision agricultural practices that use cover crops and the microbiome as levers for enhanced crop production.BPG5Z_iDvqR4KrAs2TcSTiVideo

Nitrogen transformation as affected by decomposition of 15N‐labeled cover crop shoots and roots

AbstractBackgroundIncorporation of cover crop (cc) shoot and root biomass can have different effects on nitrogen (N) dynamics and the transformation of soil‐derived N and cc N.AimsThe objective was to determine the effects of different ccs, cc compartments (roots and shoots), and pretreatment of cc biomass (fresh vs. dried) on mineralization processes and on the transformation of soil and cc N following incorporation into a silty loam soil.MethodsSoil columns with incorporated 15N‐labeled root and shoot biomass of two cc species (winter rye and oil radish) and different pretreatments (dried and fresh) were incubated for 70 days at a constant temperature and soil moisture (8°C, 40% water‐filled pore space). Carbon and N transformation dynamics were determined repeatedly, distinguishing between N originating from cc biomass and from soil.ResultsNet CO2 emission was related to the amount of soluble cell components added with ccs. Net N mineralization was negatively related to the C:N ratio of cc biomass. The incorporation of dried cc biomass caused higher initial soil respiration and N immobilization than fresh biomass. All treatments with cc incorporation showed increased N2O emission. Emitted N2O‐N consisted mainly of cc N (55%–57%) in treatments with fresh shoot biomass, whereas soil N was the main source of N2O (75%) in the treatment with fresh oil radish roots. Recovery of cc 15N was affected by crop compartment and pretreatment. At the end of the incubation, it was 17.5%–42.3% in soil NO3−, 0.1%–8.1% in microbial biomass N, and less than 0.23% of cc N was found in cumulative N2O emission.ConclusionThe incorporation of cc roots and shoots had different effects on N mobilization and immobilization processes and on the partitioning of cc N. These processes can be influenced significantly by pretreatment of the added plant biomass (dried vs. fresh).

Role of cover crop roots in soil organic carbon accrual—A review

AbstractAppropriate cover crop (CC) management is an important tool for the improvement of soil carbon stock; however, the relationships between carbon accumulation and CC root traits remain unclear. A literature review was performed to identify the extent and focus of recent research and to answer questions about the role of root traits of CCs in soil C accumulation with regard to species selection, mixture composition and agronomic management. The findings based on the analysis of 69 publications show that a range of root traits such as root biomass, architecture, depth of rooting, root chemical composition, as well as quantity and quality of rhizodeposition, can contribute to soil structure formation and C accumulation. These traits are usually species specific, and it seems that appropriate species combinations in the mixtures can offer the highest potential for optimization of C stock across various environments. However, there has been twice as much recent research on roots of CC monocultures than on mixtures, with little attention paid to agronomic aspects such as plant spatial arrangement or soil tillage in relation to CC root development. Considerations of real management under field conditions could be beneficial in providing greater accuracy of estimation of the contribution of CCs in increasing the SOC stock in croplands.

Cover crop monocultures and mixtures enhance bacterial abundance and functionality in the maize root zone.

Cover cropping is an effective method to protect agricultural soils from erosion, promote nutrient and moisture retention, encourage beneficial microbial activity, and maintain soil structure. Re-utilization of winter cover crop root channels by maize roots during summer allows the cash crop to extract resources from distal regions in the soil horizon. In this study, we investigated how cover cropping during winter followed by maize (Zea mays L.) during summer affects the spatiotemporal composition and function of the bacterial communities in the maize rhizosphere and surrounding soil samples using quantitative polymerase chain reaction (PCR), 16S ribosomal ribonucleic acid (rRNA) gene amplicon sequencing, and metaproteomics. We found that the bacterial community differed significantly among cover crop species, soil depths, and maize growth stages. Bacterial abundance increased in reused root channels, and it continued to increase as cover crop diversity changed from monocultures to mixtures. Mixing Fabaceae with Brassicaceae or Poaceae enhanced the overall contributions of several steps of the bacterial carbon and nitrogen cycles, especially glycolysis and the pentose phosphate pathway. The deeper root channels of Fabaceae and Brassicaceae as compared to Poaceae corresponded to higher bacterial 16S rRNA gene copy numbers and improved community presence in the subsoil regimes, likely due to the increased availability of root exudates secreted by maize roots. In conclusion, root channel reuse improved the expression of metabolic pathways of the carbon and nitrogen cycles and the bacterial communities, which is beneficial to the soil and to the growing crops.

Cover crop cultivars and species differ in root traits potentially impacting their selection for ecosystem services

Background and aimsCover crops have the potential to aid in adapting agricultural systems to climate change impacts through their ecosystem services, such as preventing soil erosion, remediating soil structure, and storing carbon belowground. Though roots are integral to these processes, there is a lack of cover crop root trait data. This study aims to characterize rooting behavior of several commercially available cover crops and assess how differences in root system architecture potentially impact their selection for ecosystem services.MethodsTwenty-two cover crop cultivars across the grass, legume, and brassica families were grown in O’Fallon, Missouri, USA. Canopy cover was monitored throughout the growing season. Shoot and root biomass samples were collected and analyzed.ResultsCereal rye and winter triticale were the most winter hardy cultivars and provided the highest percent canopy cover. Cereal rye and winter triticale also generated the highest amount of shoot and root biomass among treatments but diverged in their root system architectures. Winter triticale forms coarser roots and exhibited deeper rooting, which may be better suited for carbon sequestration. Rapeseed and Siberian kale have favorable C:N ratios for nutrient recycling, but rapeseed may invest more into lateral root formation and have a higher potential to “catch” excess nutrients.ConclusionSelection of cover crops for ecosystem services should account for root system architecture and their suitability for these ecosystem services. Differences in root traits among cultivars within the same family highlight the potential to breed cover crop root system architecture to further enhance ecosystem service efficacy.

Fall/winter cover crop roots change soil hydrology to control the drought status of subsequent season summer maize in Ultisol

Climate change has increased drought frequency, necessitating strategies to reduce water stress, increase water use efficiency, and improve agricultural productivity. The impacts of different fall/winter cover crops on alleviating maize drought in the subsequent season by changing soil water content remain unclear in Ultisol. Our aim was to investigate whether different fall/winter cover crops (taproot and fibrous root) can improve soil water content to attenuate subsequent season maize drought and its underlying mechanism. This research compared four fall/winter cover crops (2 rapeseed cultivars, lucerne and vetiver) and fallow control (no cover crop in winter) to investigate their root traits, root effect on subsequent season soil water content (SWC), soil drought degree (D), maize leaf and root water potential (Ψl, Ψr), maize crop water stress index (CWSI), and maize growth components (aboveground plant and root parameters) in 2019 (a dry year), 2021 (a normal wet year), and 2022 (a severe dry year). The fibrous-rooted vetiver displayed higher average root diameter and higher average root length density, leading to increased SWC (17%, 15%, 15%), and lower D values in all three years. Additionally, it exhibited a more substantial gradient between Ψl, and Ψr and lower CWSI than taproot (rapeseed cultivars and lucerne) and fallow treatment. Furthermore, the cover crop treatments enhanced the gradient between maize Ψl and Ψr to varying degrees in different drought years. Ultimately, the improvement in SWC resulting from cover crop treatments increased maize aboveground growth (plant height, stem diameter, and leaf area) and maize root development, ultimately improving maize yield. This study introduces a new perspective on investigating the role of cover crops in alleviating seasonal drought in subsequent crops, especially by changing soil water properties in the subtropical climate.

Effect of soil compaction and cover crop management on soil physical quality, biomass production and corn and soybean yield

ABSTRACT No-till with cover crop (CC) has been marketed to growers as a sustainable way to increase soil quality and crop yields. Our goal was to better understand the effect of CC management strategies on crop yield and mitigation of soil compaction. The compaction treatments were: four (C4) and eight (C8) wheel passes of a tractor, and without additional compaction (C0). CCs in autumn/winter were Italian ryegrass (IR) hay, IR as CC, and mix of IR and forage radish as CC. In the spring/summer, corn and soybean were cultivated. The reduction of hydraulic conductivity (0–6 cm depth) after first season in the IR hay was 74.9% in C4 and 96.2% in C8 comparted with C0. Overall, harvested CC has limited capacity to respond to compaction, decreasing root growth (root biomass of 2191, 2753, and 3744 kg ha−1, IR hay, IR CC, and mix, respectively). Further, the negative effects of compaction on crop yield were modest, probably because of the low axle loads and contact stresses; high inherent structural stability of Oxisols; and permanent no-till and CC roots which favored soil structure stability. Future works should use higher axle loads and surface stresses and a control treatment without CC.

Cover crop root morphology rather than quality controls the fate of root and rhizodeposition C into distinct soil C pools.

Cover crops increase carbon (C) inputs to agricultural soils, and thus have the potential to mitigate climate change through enhanced soil organic carbon (SOC) storage. However, few studies have explored the fate of belowground C inputs associated with varying root traits into the distinct SOC pools of mineral-associated organic carbon (MAOC) particulate organic carbon (POC). Therefore, a packed 0.5 m column trial was established with 0.25 m topsoil and 0.25 m subsoil with four cover crops species (winter rye, oilseed radish, chicory, and hairy vetch) known to differ in C:N ratio and root morphology. Cover crops were 14 CO2 -labeled for 3 months, and then, half of the columns were sampled to quantify root and rhizodeposition C. In the remaining columns, plant shoots were harvested and the undisturbed soil and roots were left for incubation. Bulk soil from both sampling times was subjected to a simple fractionation scheme, where 14 C in the <50 and >50 μm fraction was assumed to represent MAOC and POC, respectively. The fast-growing rye and radish produced the highest root C. The percentage loss of C via rhizodeposition (%ClvR) showed a distinct pattern, with 22% for the more branched roots (rye and vetch) and 6%-8% for the less branched roots (radish and chicory). This suggests that root morphology plays a key role in determining rhizodeposition C. After 1 year of incubation at room temperature, the remaining MAOC and POC were positively correlated with belowground inputs in absolute terms. However, topsoil MAOC formation efficiencies (cover crop-derived MAOC remaining as a share of belowground inputs) were higher for vetch and rye (21% and 15%, respectively) than for chicory and radish (9% and 10%, respectively), suggesting a greater importance of rhizodeposition (or indirectly, root morphology) than solely substrate C:N ratio for longer term C stabilization.

Combined impact of no-tillage and cover crops on soil carbon stocks and fluxes in maize crops

Soil plays a major role in the carbon cycle for both carbon stocks and respiration since soil organic carbon (SOC) is the most important carbon pool and soil CO2 efflux is the largest source of carbon emissions to the atmosphere. The aim of this study was to understand how the combination of no-till (NT) and cover cropping (CC) influences both SOC and soil respiration. Soil respiration was measured in southwestern France from April to October at two distinct sites characterized by contrasting initial soil carbon contents. Each site included two adjoining maize fields in which conservation (NT+CC) and conventional (CT) practices were used. For soil with initial high SOC contents (> 50 tC ha-1 in the 0–30cm layer), SOC stocks at the 0–90 cm depth (NT+CC: 72.4 ± 10.6, CT: 68.9 ± 9.2 t C ha-1) and respiration during the maize growing season (NT+CC: 0.57 ± 0.24, CT: 0.54 ± 0.26 g CO2 m-2 h-1) were not significantly different for both practices. For soil with initial low SOC contents, SOC stocks at the 0–90 cm depth (NT+CC: 42.7 ± 5.5, CT: 29.7 ± 4.8 t C ha-1) and respiration (NT+CC: 0.86 ± 0.32, CT: 0.50 ± 0.34 g CO2 m-2 h-1) were higher with the NT+CC practices than with the CT practices. Due to higher cover crop biomass and root density, SOC mineralization and root respiration were enhanced. We showed a positive effect of conservation practices on the SOC stock in the upper layers but also in the deeper layers (60–90 cm) only in a low initial carbon content environment. At high SOC levels, the soil may have reached its carbon sequestration potential, or the time since practices were implemented was not long enough to observe the effects. Our study shows that the potential of NT+CC to sequester large amounts of SOC, enabling the mitigation of greenhouse gas emissions, strongly depends on initial SOC contents.

Influence of Two Cover Crops (Arachis repens L. and Desmodium adscendens Sw.) on Root Infestation of the “Great Dwarf” Dessert Banana Cultivar (Musa sp.) by Plant-parasitic Nematodes in Southeast Côte d’Ivoire

Context: In Côte d’Ivoire, industrial banana plantations are faced with the problem of weediness. However, the use of herbicides as a means of control presents significant risks for human health and the environment. The abandonment of these products for more ecological alternatives such as cover crops is imminent.&#x0D; Aims: This study aimed to compare the relative abundance and the density of the main plant-parasitic nematodes in the roots of banana and cover crops according to three weed management treatments.&#x0D; Study Design and Methodology: The experimental design was a three-repeat Fisher block of three treatments consisting of implementation of A. repens and D. adscendens as cover crops and spraying of two synthetic herbicides (glufosinate and glyphosate) for weed management. The relative abundance and density of nematodes in the roots of banana and cover crops were assessed quarterly after extraction by the rapid double centrifugation-flotation method and enumeration under an optical microscope.&#x0D; Results: Both cover crops and banana plants had their roots infested by the major parasitic nematodes evaluated (Radopholus similis, Pratylenchus spp., Helicotylenchus spp., Meloidogyne spp., Rotylenchulus reniformis and Hoplolaimus pararobustus). These infestations were not a function of weed management treatments. Compared to the use of herbicides, A. repens and D. adscendens used as ground cover did not significantly increase or decrease nematode dynamics in the plots. Individuals extracted from the roots of the cover crops, and particularly from D. adscendens, were more numerous than from the roots of the banana plants. In terms of proportions, Pratylenchus spp., R. similis, Helicotylenchus spp. and Meloidogyne spp. were most abundant. R. reniformis and H. pararobustus as well as various nematodes (plant parasites: Hirschmanniella spp., Xiphinema spp., ..., and non-plant parasites: fungivorous, carnivorous, bacterivorous, ...) were in the minority.&#x0D; Conclusion: The results, particularly those of A. repens, could be useful in the biological, ecological and sustainable management of weed in banana plantations without important risks of pest pressure.

Reaction of Winter Cover Crops to Meloidogyne enterolobii and Glasshouse Bioassay for Evaluating Utility in Managing M. enterolobii in Soybeans.

Meloidogyne enterolobii is an invasive and highly aggressive root-knot nematode pathogen impacting the Southeastern United States. Winter cover cropping may be a cost-effective method for reducing populations of M. enterolobii in between summer cash crops, yet a gap in the knowledge remains about the response of these cover crops to M. enterolobii and their utility in suppressing nematode populations prior to a cash crop. A "two-step" glasshouse bioassay was performed to evaluate eight winter cover crops popular in North Carolina for their direct response to M. enterolobii infection, and to quantify their effect in reducing nematode populations for the following soybean plants. Data on cover crop root galling, soybean root galling, soybean shoot fresh weight, soybean root fresh weight, eggs per gram of soybean root, and a modified reproductive factor were collected. Cereal cover crops did not display root galling, and there was significantly less root galling in those soybean plants following cereal winter cover crops when compared to those following broadleaf winter cover crops. Broadleaf winter cover crops resulted in significantly higher eggs per gram of soybean root and modified reproductive factor in the soybean plants, compared to cereal cover crops and non-inoculated controls. Results from this study suggest that cereal winter cover crops may be poor-hosts to M. enterolobii and may significantly reduce M. enterolobii populations before a soybean crop, compared to broadleaf winter cover crops. This study lays the groundwork for management recommendations and future field trials to assess management of M. enterolobii through winter cover cropping.

Cover crop root-derived organic carbon influences aggregate stability through soil internal forces in a clayey red soil

Soil aggregate stability is influenced by soil organic carbon (SOC). However, the influence of SOC from different fall/winter cover crop roots (annual and perennial crops) on aggregate stability through soil internal forces (SIFs) (electrostatic repulsive force (Perf), van der Waals attractive force (Pvdw), and surface hydration repulsive force (Ph)) remains unclear. The objectives of this study were compare three fall/winter cover crops (lucerne, rapeseed, six-year-vetiver (Vet_6Y)) and two control (fallow and fallow with SOC removal (fallow-SOC-R)) to determine SOC effects red soil aggregation through SIFs. Plant root morphological and chemical traits, SOC properties, soil surface charge properties, soil internal forces and aggregate breakdown were all determined. The perennial crop (Vet_6Y) showed the highest root number density (0.21 counts cm−2), second highest root mass density (1.80 mg cm−3), and the lowest root lignin/cellulose ratio (0.69), and thus contributed to higher SOC content and SOC functional groups (mainly polysaccharide-C) than annual crops (rapeseed and lucerne). Such SOC traits in perennial vetiver resulted in a higher specific surface area (SSA), lower surface charge density and surface charge number (Qs) compared to annual crops (rapeseed and lucerne) and controls, and the relationship between the root, SOC and soil surface properties (i.e., SSA) was further confirmed by significant correlation (r ranging from 0.76 to 0.97). Ultimately, these soil surface charge properties after cover crops increased Pvdw, decreased Perf, and thus decreased repulsive net force (Pnet) (the sum of Pvdw, Perf, and Ph) and the average repulsive net force displayed in order of fallow-SOC-R (2.77 MPa) > fallow (2.11 MPa) > lucerne (2.02 MPa) > rapeseed (1.78 MPa) > Vet_6Y (1.45 MPa) at a distance of 1 nm. This resulted in the mass percentage of released small particles (<20, <10, and <2 µm) w (<d) % from aggregate being reduced after cover crops compared to controls. Generally, clayey red soil aggregate stability can be improved by decreasing the repulsive soil Pnet through cover crop root contribution to SOC and SOC-functional groups.

Cover crop effects on soil structure and early sugar beet growth

AbstractCover crops can improve soil properties, especially soil structure, through organic matter input and rooting activity. However, large variations exist among cover crops, which may lead to differences in the extent of these effects. In this study, cover crops with differing properties were compared regarding soil structure and subsequent sugar beet growth. Field experiments were conducted at two Luvisol sites in Central Germany. Four cover crops (oil radish, saia oat, spring vetch and winter rye) were compared with fallow. Cover crop effects on soil water, Nmin content, soil structure and subsequent early sugar beet growth were studied. Additionally, sugar beet received either no or optimal N fertilizer application. Rye and radish had the highest and vetch the lowest above‐ and belowground biomass. Soil water content was hardly affected by cover cropping, while topsoil Nmin contents in April were increased. Penetration resistance was lowered, and aggregate stability was increased by the cover crops, especially oil radish, while values after spring vetch were similar to those of fallow. Differences among the cover crops might be because of a differing root biomass. Independent of N fertilizer application, sugar beet biomass in May tended to be higher after all cover crops, in particular under oil radish. The higher aggregate stability and lower penetration resistance were found to be beneficial for early sugar beet growth. Thus, sugar beet can benefit from a 1‐year cultivation of preceding cover crops. Modifications of this effect through cover crop root biomass and architecture as well as repeated cover cropping need to be investigated in further studies.

Different fall/winter cover crop root patterns induce contrasting red soil (Ultisols) mechanical resistance through aggregate properties

Different fall/winter cover crop root patterns induce contrasting red soil (Ultisols) mechanical resistance through aggregate properties

The role of microbes in the increase of organic phosphorus availability in the rhizosheath of cover crops

Background and aimsThe characterisation of plant-available phosphorus (P) pools and the assessment of the microbial community in the rhizosheath of cover crops can improve our understanding of plant–microbe interactions and P availability.MethodsMustard (Sinapis alba), phacelia (Phacelia tanacetifolia) and buckwheat (Fagopyrum esculentum) were grown as cover crops before soybean (Glycine max) in an on-farm experiment on a soil low in available P in southwest Germany. The cycling of P through the cover crop biomass and the enzyme-availability of organic P (Porg) pools in the cover crop rhizosheath were characterised. The soil microbial community (PLFA), activity (acid and alkaline phosphomonoesterase, as well as phosphodiesterase), and microbial P were assessed. The abundance of 16S-rRNA and phoD, coding for alkaline phosphomonoesterase in bacteria, were quantified using real-time qPCR.ResultsMustard contained the greatest amount of P in its large biomass. In the rhizosheath of all cover crops, the concentration of enzyme-labile Porg was higher than that in the control bulk soil, along with substantial increases of microbial abundance and activity. There were little differences among cover crop species, few changes in the bulk soil and only a limited carryover effect to soybean, except for fungi.ConclusionsTurnover of microbial biomass, especially saprotrophic fungi, increased by rhizodeposition of cover crop roots; this was likely responsible for the observed increases in enzyme-available Porg. Microbial function was correlated linearly with microbial biomass, and the data of enzyme activity and phoD did not suggest a difference of their specific activity between bulk and rhizosheath soil.

Bio‐tillage improves soil physical properties and maize growth in a compacted Vertisol by cover crops

AbstractBio‐tillage has recently been proposed as a measure to alleviate soil compaction through biopores created by cover crop roots. The objective of this study was to determine the effect of different cover crops on soil physical properties and the succeeding maize (Zea mays L.) growth in compacted soil. Four treatments, including no cover crop as a control (Con), alfalfa (Medicago sativa L.), oilseed rape (Brassica napus L.), and radish and hairy vetch mixture (Raphanus sativus L. and Vicia villosa Roth), were carried out under both compacted and noncompacted soil conditions. Soil physical properties, such as the volumetric soil water content (SWC), bulk density, saturated hydraulic conductivity (Ks) and air permeability at water potential of −60 hPa (Ka60), and maize root characteristics and yield were measured. The cover crops did not affect the soil bulk density but significantly decreased the SWC in both the compacted and noncompacted soils relative to the Con treatment. The alfalfa treatment presented significantly higher Ks in the noncompacted soil and Ka60 in both the compacted and noncompacted soils than the Con treatment in the soil layer depth of 20–50 cm. The three cover crop treatments improved the maize root biomass density (173.2% for 2018 and 35.6% for 2019) and root length density (50.9% for 2018 and 51.8% for 2019) relative to the Con treatment in the soil layer depth of 10–70 cm in 2018 and soil layer depth of 10–50 cm in 2019 in the compacted soil rather than in the noncompacted soil. Compared with the Con treatment, the radish mixed with hairy vetch treatment in 2018 and the oilseed rape treatment in 2019 significantly enhanced the maize yield in the compacted soil. Our results suggest that alfalfa is the best crop for improving air permeability; however, the oilseed rape and mixture of radish and hairy vetch lead to better maize growth in the compacted soil. Bio‐tillage using cover crops is effective in alleviating soil compaction.

Optimisation of root traits to provide enhanced ecosystem services in agricultural systems: A focus on cover crops.

Roots are the interface between the plant and the soil and play a central role in multiple ecosystem processes. With intensification of agricultural practices, rhizosphere processes are being disrupted and are causing degradation of the physical, chemical and biotic properties of soil. However, cover crops, a group of plants that provide ecosystem services, can be utilised during fallow periods or used as an intercrop to restore soil health. The effectiveness of ecosystem services provided by cover crops varies widely as very little breeding has occurred in these species. Improvement of ecosystem service performance is rarely considered as a breeding trait due to the complexities and challenges of belowground evaluation. Advancements in root phenotyping and genetic tools are critical in accelerating ecosystem service improvement in cover crops. In this study, we provide an overview of the range of belowground ecosystem services provided by cover crop roots: (1) soil structural remediation, (2) capture of soil resources and (3) maintenance of the rhizosphere and building of organic matter content. Based on the ecosystem services described, we outline current and promising phenotyping technologies and breeding strategies in cover crops that can enhance agricultural sustainability through improvement of root traits.

A Characterization of a Cool-Climate Organic Vineyard’s Microbiome

The microbiome, an influential factor affecting plant health and growth, is attracting increasing interest with respect to wine grape production. The purpose of this study was to characterize the microbiome (fungi and bacteria) of the soil, cover crop roots, and grape (Vitis spp.) roots across rootstock and depth in a cool-climate, organic vineyard. The cover crop consisted of a fescue (Festuca sp.) grass, while grape roots were sampled from New York Muscat, a cool-climate hybrid, across three root types (ungrafted, 3309C and Riparia Gloire) at three root depths (0 to 15, 15 to 30, and 30 to 50 cm). The grape root microbiome was more specialized, with fewer observed amplicon sequence variants for both bacteria (16S) and fungi (internal transcribe spacer) than found in the cover crop and the surrounding soil. Grape roots were dominated by bacterial genera Pseudomonas, Niastella, and Rhizobium; most prominent fungal genera were Plectosphaerella, Trichosporon, and Ilyonectria. Although no correlations were found between α-diversity metrics and soil parameters, Pseudaleuria relative abundance was correlated with Mn, Fe, and Na levels. Soil depth explained a small portion of bacterial but not fungal variance and taxonomic composition. Rootstock type explained a portion of both bacterial and fungal variance and taxonomic composition, substantiating the role of host plant genetics in the development of the grape root microbiome. This is the first characterization of the grape root microbiome in a cool-climate Canadian vineyard.

Site‐specific effects of winter cover crops on soil water storage

AbstractAddition of an overwintering cereal rye (Secale cereale L.) cover crop (CC) to midwestern maize (Zea mays L.)‐based systems offers several environmental benefits, but the long‐term effects of this practice on soil hydrological properties are not well understood. We utilized four long‐term (10+ yr) trials (two commercial fields, two research plots) in Iowa that included a replicated winter rye CC and no‐cover treatment in no‐till maize/soybean [Glycine max (L.) Merr.] systems. We took intact 7.62‐cm diam. soil samples from a 10‐to‐18‐cm depth shortly after cash crop planting in the spring. We measured the soil water retention curve using matric potentials ranging from saturation to –500 cmH2O. In addition, we measured organic matter, textural composition, and bulk densities of the soil samples. At the depth sampled, CCs did not meaningfully affect bulk density, water contents at saturation, or air‐entry potentials at any trial, nor increase the percentage of macropores. At two trials, soil water content at field capacity (–100 cmH2O) in the CC treatments was 2.5 vol% (SE: 1.2%; commercial field) and 2.4 vol% (SE: 1.3%; research plot) higher compared with the no‐cover treatments. This increase could meaningfully reduce the amount of water drained from a field after a saturating rain and should be considered when assessing CC impacts on landscape hydrology. The presence or absence of a CC effect on field capacity was not related to CC aboveground biomass production, previous cash crop, or soil texture at the trial sites. Based on our results, a causal model, and previous literature we hypothesize CC root characteristics are key to understanding variable effects of CCs on soil water storage. Our results indicate it is possible for CCs to meaningfully affect soil water storage, but more research is needed on the mechanisms by which these changes occur.

Influence of Spatial Planting Arrangement of Winter Rye Cover Crop on Corn Seedling Disease and Corn Productivity.

Despite numerous environmental benefits associated with cover crop (CC) use, some farmers are reluctant to include CCs in their production systems because of reported yield declines in corn. There are numerous potential reasons for this yield decline, including seedling disease. A winter rye CC can serve as a "green bridge" for corn seedling pathogens. We hypothesized that proximity of corn seedling roots to decaying rye CC roots contributes to corn seeding disease. An experimental field plot and an on-farm study were conducted over 2 years to evaluate growth, development, and disease severity of corn seedlings planted at various distances from decaying winter rye CC plants. The experimental field plot study was conducted in a no-till corn-soybean rotation with five replications of a winter rye CC treatment seeded as (i) no-CC control, (ii) broadcast, (iii) 19-cm drilled rows, and (iv) 76-cm drilled rows. The on-farm study was no-till corn-soybean rotation with four replications of a winter rye CC seeded as 38-cm drilled rows, 76-cm drilled rows, and no-CC control. The corn was planted on 76-cm rows shortly after rye was terminated. With multiple seeding arrangements of winter rye, corn was planted at different distances from winter rye. Corn radicle root rot severity and incidence, shoot height, shoot dry weight, corn height and chlorophyll at VT (tasseling), ear parameters, and yield were collected. Soil samples were taken in the corn row and the interrow at winter rye termination, corn planting, and corn growth stage V3 (three leaves with fully developed collars) to estimate the abundance of Pythium clade B members present in soil samples. Our results showed that increased distance between winter rye residue and corn reduced seedling disease and Pythium clade B populations in the radicles and soil and increased shoot dry weight, leaf chlorophyll, plant height, and yield. This suggests that physically distancing the corn crop from the winter rye CC is one way to reduce the negative effects of a winter rye CC on corn.